This invention pertains to the art of fluid actuators and more particularly to a new and improved end cap assembly for such actuators.
The invention is particularly applicable to an end cap assembly for an air actuator used to selectively operate a fluid shut-off valve and will be described with continued reference thereto. However, it will be readily appreciated by those skilled in the art that the invention has far broader applications and may be adapted for use in a wide variety of environments where an end cap assembly is employed and where it is desired to place an axial clamping force on some component while eliminating any corresponding rotational forces.
The general types of actuators to which the present invention is particularly adapted for use are shown in the commonly assigned U.S. Pat. Nos. 3,312,446 and 3,354,897, the teachings of which are incorporated hereinto by reference. Both of these patents show actuators which include an actuator body having an end cap threadedly received over the outer end thereof. In both cases, a flexible diaphragm is fixedly captured between the outer or upper end area of the body and a portion of the cap. However, when the cap is installed, undesirable rotational or twisting forces are applied to the diaphragm which can adversely affect diaphragm operation or shorten its effective life. Moreover, these prior constructions do not provide means for compensating for variations in diaphragm thickness which may occur as a result of temperature or other environmental conditions. If the diaphragm thickness decreases, it may become loosened in its captured or clamped position and adversely affect actuator operation. The only means available to overcome this problem is to monitor continually the actuators and retighten the end cap when and as required. Such tightening, however, further increases the rotational or twisting forces applied to the diaphragm which, as previously noted, is highly undesirable.
It has, therefore, been considered appropriate to develop an actuator end cap construction which would prevent the application of rotational or twisting forces to the diaphragm as the end cap is installed. Also, such a construction should eliminate the necessity for constant monitoring to insure maintenance of proper adjustment.
The present invention contemplates a new and improved device which overcomes the foregoing problems and others and provides an end cap assembly which is simple in design, effective in use, which automatically compensates for diaphragm thickness variations, accommodates application of an effective axial clamping force against the diaphragm and which is readily adaptable to use in a wide variety of alternative applications and/or environments.